The present invention relates to a vehicle passenger seat air bag module having a housing, an air bag sack, an air bag sack inflating device, and a deployment opening cover assembly, whereby the deployment opening cover assembly, in the event of a deployment of the air bag sack through the deployment opening, is withdrawn behind the instrument panel or dashboard by a drive mechanism and whereby the drive mechanism comprises a cylinder and piston arrangement which is powered by a pressurized fluid device separate from the air bag sack inflating device which inflates the air bag sack.
An air bag module of the general type described above is disclosed in EP 0 867 346 A1. The deployment opening cover assembly, which is built into the instrument panel, includes a pair of cover elements which are normally closed and which, in the event of an air bag deployment, are drawn apart from one another by means of a drive mechanism, each to a respective withdrawn position behind the deployment opening of the module housing. In this regard, a pull cord secured to each respective covering element acts as a pulling force transmitting element; the two pulling cords are movable via linkages into a guide cylinder located rearwardly in the interior of the module housing by actuation of two oppositely driveable rods. In one embodiment of this known air bag module, the driving of the rods is accomplished via a special gas generator.
Known air bag modules bring with them the drawback that their overall construction is complicated due to the integration in the module housing of the drive arrangement, which drives the pulling force transmitting element, and the significant effort required for the installation of such drive arrangements. In view of the fact that the opening mechanisms for the one or several cover elements for various types of motor vehicles have differing requirements, adaptation of the air bag modules to the differing layout requirements is scarcely possible or possible only with a corresponding installation effort. Due to the connection of the pulling force transmitting element to the drive arrangement in the interior of the module housing, such known configurations can lead to compromises in the sealed status of the air bag modules in the areas of the housing wall of the module housing through which the pulling force transmitting element extends.
The present invention offers a solution to the challenge of providing an air bag module having a flexible configuration for adapting the air bag module to differing vehicle constructions.
The air bag module of the present invention incorporates the basic concept that the drive mechanism for moving the deployment opening cover assembly is located in a special housing in which a plurality of drive pistons are disposed in proximity to a gas generator with the drive pistons being operable to move at least one push bar outwardly from the housing such that the push bar translates the movement imparted to it by the drive pistons onto a pulling force transmitting element trained around the housing, thereby causing the pulling force transmitting element to withdraw the deployment opening cover assembly from its deployment opening covering position.
The present invention has the advantage of offering the possibility of accommodating the drive mechanism to its installation location in the vehicle by virtue of the effective separation of the air bag containing module from the drive mechanism for driving the opening of the deployment opening cover assembly. Since the drive block of the drive mechanism is configured as a closed system, the drive mechanism can be configured, without the danger of seal leakage, for a correspondingly higher working pressure of the type which can be useful in individual cases for the opening of the deployment opening cover assembly in the instrument panel of a motor vehicle. To the extent that the drive mechanism need only be configured for the requirements of effecting the uncovering of the deployment opening, the drive mechanism can be configured in a compact and space-saving arrangement. Since the arrangement and dimensions of the selected plurality of cylinder bores with their associated drive pistons can be varied, it is possible to configure the drive arrangement in a manner which takes into account the withdrawal movement of a single cover element deployment opening cover assembly or the withdrawal movements of a multiple cover element deployment opening cover assembly, whereby the number and individual diameters of the drive pistons associated with a given cover element, and the corresponding effective drive force needed to effect withdrawal movement of the cover element, can be customized or individually accommodated. It is thus possible, with a uniform working pressure in the drive block, to transfer forces to individual cover elements which are different from the forces transferred to other individual cover elements. Individually different outward movement paths of the pulling force transmitting elements connected to the cover elements can be configured into the drive mechanism by individual specific dimensioning of the length of the cylinder bores having the drive pistons therein in combination with a travel limit construction built into the drive block for limiting the outward movement of the push bars acting on the pulling force transmitting element or pulling force transmitting elements. At the same time, the arrangement of the special drive block makes it possible to move individual cover elements in a leading or trailing manner.
In accordance with one embodiment of the air bag module of the present invention, it is provided that the special drive block is mounted on the module housing such that the advantageous possibility exists that the individually customized drive block can be connected to a more fully or, alternately, a less fully, standardized module housing.
In accordance with one embodiment of the air bag module of the present invention, it is provided that the manifold, which commonly communicates a gas generator of the drive mechanism with the cylinder bores in the drive block, has a reduced cross section portion; in this manner, it is possible to selectively set the dynamic forces which are operable on the deployment opening cover assembly.
Overflow openings are provided each in a respective cylinder bore of the drive block at a spacing from the junction of the manifold and the respective cylinder bore such that the piston driving pressurized fluid in the respective cylinder bore is released upon passage of the associated drive piston past the overflow opening. This places the respective cylinder bore in a depressurized condition and is a means by which a limit can be placed on the outward movement of the push bar connected to the associated drive piston.
The present invention provides, as another approach to limiting outward movement of the push bar in addition to, or in lieu of, the overflow openings, that the push bar, which is pushed outwardly from the drive block, is limited in its travel by an outward travel limit element which applies its travel limiting action once a predetermined outer travel limit is reached.
In view of the fact that typical deployment opening cover assemblies for motor vehicles, which operate to cover the air bag deployment opening that is located in the instrument panel, can have a considerable width, it is provided, in accordance with one embodiment of the air bag module of the present invention, that two pulling force transmitting elements are connected to the deployment opening cover assembly. It can further be provided, in accordance with the present invention, that the plurality of drive pistons are connected to the associated push bar in the area in which the pulling force transmitting element is trained over the push bar. To ensure that the cover elements of the deployment opening cover assembly are moved in a uniform manner into their respective withdrawn positions, it is provided that, within the drive block, the cylinder bores are arranged symmetrically relative to the gas generator which is located centrally in the drive block.
The present invention, in its basic configuration, is sufficient for withdrawing a single cover element deployment opening cover assembly from its deployment opening cover position, whereby the one or several pulling force transmitting elements are connected to the cover element and are trained around and fixedly connected to the module housing in a manner such that the movement of the push bar outwardly from the drive block leads to a taking up or tightening of the pulling force transmitting elements which operates to withdraw the cover element away from its deployment opening cover position in the direction of the module housing.
To the extent that the deployment opening is covered by two cover elements which are withdrawable in mutually opposite directions from one another to thereby uncover the deployment opening, it is advantageous, in accordance with one embodiment of the air bag module of the present invention, if the deployment opening cover assembly is comprised of the two cover elements and that a respective end of the pulling force transmitting element is secured to each cover element. It is similarly advantageous, in accordance with one embodiment of the air bag module of the present invention, if two push bars are provided, each movable outwardly from the housing in a direction opposite to that of the other push bar; in this configuration, each push bar can be connected, for example, to a plurality of drive pistons which are movably retained in associated cylinder bores communicated with a gas generator that provides piston driving pressurized fluid.
In connection with limiting the movement of the push bars outwardly from the drive block, which movement effects a shortening of the effective length of the pulling force transmitting element, the assembly or construction of the drive block can be reduced if a doubling up or looping back of the pulling force transmitting element is provided since the pulling force transmitting element is trained around the housing in a manner such that outward movement of the push bars leads to the creation of a loop in the pulling force transmitting element.